radars

3. an electronic device that can increase the power of a signal
4. used when it is possible to transmit and receive simultaneously
5. an arrangement of resistors which reduces the strength of a radio or audio signal
6. in radio amateur use, bi-directional communication on a single frequency
8. typically an electrical transformer used to connect an unbalanced circuit to a balanced one
10. the direction of a magnetic or electrical field
12. a device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator
14. a horizontal dipole fed at the centre with parallel wire transmission line
16. an instruments for converting sound waves into electrical energy
17. an array of dipole antennas mounted in such a manner that every element of each antenna is in an extension, with respect to its long axis, of its counterparts in the other antennas in the array, usually mounted vertically in order to increase overall gain and directivity in the horizontal direction

1. used for measuring the input impedance of antenna systems in radio applications
2. the behaviour of radio waves as they travel from one point to another
4. an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated carrier wave
7. the process of configuring an instrument to provide a result for a sample within an acceptable range
9. a specific range of frequencies in the radio frequency spectrum
11. one or more cells, in which chemical energy is converted into electricity and used as a source of power
13. the layer of the earth's atmosphere which contains a high concentration of ions and free electrons
14. an aerial consisting of two poles or sections to the radiating element - in its most common it is a half-wavelength long at the frequency of operation
15. two concentric conductors separated by an insulator
17. used to generate electricity, or one that is used to make chemical reactions possible by applying electricity